1. Field of the Invention
The present invention relates to a design support system, a design support method and a computer readable record medium on which a program for use in those system and method is recorded, for supporting designing of facilities such as base stations in mobile communication systems such as cellular communication systems.
2. Description of the Related Art
A mobile communication system such as a cellular communication system comprises a plurality of base stations disposed within service areas and a plurality of mobile stations to communicate with the base stations. In such a mobile communication system, the number of mobile stations which allows simultaneous communications without causing deterioration of communications quality, that is, traffic capacity, largely depends on radio wave propagation environment, transmission power of base stations, interference from other mobile stations in simultaneous communications, and so on.
Improper design of mobile communication system facilities would not only cause inefficiency in the mobile communication system, but also cause such problems as to prevent provision of desired service areas and a desired traffic capacity.
A mobile communication system constructed on the basis of improper design of mobile communication system facilities disadvantageously provides deteriorated service quality, such as causing forced disconnection during communications.
For these reasons, it is important to optimize the locations of base stations and system parameters regarding transmission power and the like by, for example, increasing transmission power to an extent not causing interference between mobile stations so as to configure an efficient mobile communication system with a smaller number of base stations and increased traffic capacities in all service areas.
However, the optimization of locations of base stations and system parameters as described above is not easy because of complicated effects of many factors such as radio wave propagation, interference between mobile stations and traffic characteristics.
In order to solve those problems, a design support tool (such as software or a device) for estimating propagation environment, communications quality and the like is used for supporting designing of mobile communication system facilities. Such a design support tool estimates a propagation loss in radio wave propagation, the amount of interference between mobile stations, a signal-to-interference ratio (SIR), and the like by computing. A designer for mobile communication system facilities can input the locations of base stations and system parameters into the tool, performing computation required for the designing of the mobile communication system facilities, and thereby obtaining evaluation results.
A design support tool for processing measured data has been conventionally used for the support of designing of mobile communication system facilities and service quality management in mobile communication systems. Such a design support tool can process real-world measurement results such as an electric field intensity, the amount of interference and an SIR by computer, map the measured values on a map, and provide statistics.
A designer, using the design support tool, views estimation results such as a propagation loss and an SIR or computational results, and adjusts system parameters by his own judgment, repeating evaluations on the design result of the mobile communication system facilities, and thereby optimizing the design of the mobile communication system facilities.
However, this optimization of mobile communication system facilities using the conventional design support tool requires consideration given to many factors such as a propagation loss, the amount of interference between mobile stations, an SIR, traffic characteristics and geographical distribution during the adjustment of system parameters.
The optimization involves, in addition to the locations of base stations, a number of system parameters such as antenna directivity, transmission power of each radio channel and hand over thresholds. The optimization of a number of system parameters by a designer's judgment involving simultaneous analysis of various estimation results thus requires cut-and-try complicated work, requiring much effort and high degree of experience of an operator.